298 results about "Slip frequency" patented technology

The invention relates to a method for recognizing parameters of asynchronous motor. The stator resistance of motor is measured by a method of DC volt-ampere. The rotor resistances as well as leakage inductance of stator and rotor of motor is obtained by short circuit test. Mutual inductance of stator and rotor of motor can be taken from method of no-load test. Compensating voltage drop in on state, switch time delay and dead time raises the accuracy and stability of recognized parameter. The resistance values of rotor at frequency of rating sliding difference are calculated by method of two points through test of locked rotor at two frequencies. Since skin effect is overcome, the resistance values of rotor are accurate enough so as to meet the requirement of vector control system completely.

The invention discloses a cooperative control method for a wind power plant and a flexible direct current transmission system for improving an inertial level of a power system. The control method is used for simulating the inertia of a synchronous generator by virtue of a direct-current capacitor and the kinetic energy of a DFIG (Doubly Fed Induction Generator) rotor. The cooperative control method comprises the steps that a GSVSC (Grid-Side Voltage Source Converter) enables the direct-current capacitor to correspondingly absorb or release energy through the slip frequency control on a direct-current voltage under the disturbance of a power grid; then, a WFVSC (Wind Field Voltage Source Converter) converts the changed direct-current voltage into a wind field side alternating-current system change frequency signal through frequency conversion control after feeling the fluctuation of the direct-current voltage, so that a maritime alternating-current system and a shore alternating-current system are artificially coupled, and the communication between convertor stations at two ends is omitted; finally, a power instruction value is adjusted by a DFIG power controller in order to respond to the frequency change of the WFVSC, and the rotating speed of the rotor is also correspondingly changed. Through a series of cooperative control, a maritime wind field takes part in the frequency adjustment of a power system so as to play an important significance to the introduction of a large maritime wind field.

The invention discloses a method for estimating a rotor position of a three-stage brushless AC synchronous motor. A main exciter of the three-stage brushless AC synchronous motor is a three-phase field winding, and a three-phase alternating current is connected to the three-phase field winding, wherein the three-phase alternating current acts as the three-phase exciting current of the main exciter; the slip frequency of exciting magnetic potential and motor rotors is set as one-sixth of the high-frequency signal frequency that is expected to be injected; and after the alternating current induced at the rotor side passes a rotary rectifier, a DC current with high-frequency harmonic components is generated so as to provide excitation for the main generator field winding, detect output current of the main generator, and realize the determination of the initial motor rotor position and the estimation of the rotor position during the starting operation. By use of the method for estimating the position disclosed by the present invention, a more accurate position estimation value can be obtained, and the method is insensitive to the accuracy of the injected high-frequency signal frequency and phase, and has certain anti-interference ability.

The invention discloses a low voltage ride-through control method of a doubly fed induction aero-generator, which is used when a power network has short circuit faults. The control method is characterized in that a rotor exciting voltage positive-sequence control current and a rotor exciting voltage negative-sequence control signal are respectively formed through limiting a rotor slip frequency current and a rotor (2-s) rated frequency current when the power network has faults, and a generator is utilized for realizing the attenuation of stator flux transient DC components and reducing the rotor side influences of the stator flux transient components, positive-sequence components and negative-sequence components. The control method has the advantages that no hardware protecting device is required to be added; under the condition that the power network has symmetrical and asymmetrical faults, the overcurrent occurrence of the rotor can be effectively restrained, and the safe operations of the generator and a rotor exciting converter are protected; in the process that the power network has the faults, the transient generator impact to the power network and a mechanical system can be effectively reduced; the normal operation of the generator can be fast recovered after the faults are removed, and the timely support to the power network can be realized.

The invention belongs to the field of controlling a power conversion device of a wind driven generator, relating to a rotor current control method of a double-fed wind driven generator under power grid faults. The method comprises the following steps: obtaining the stator voltage and the rotor current under a two-phase static coordinates by utilizing the detected three-phase stator voltage and the three-phase rotor current through a 3/2 conversion module; calculating the stator magnetic flux linkage and the position angle; calculating the slip frequency angle and the slip frequency angular velocity; summating the stator magnetic flux linkage position angle and the rotor position angle, and then carrying out differentiation to obtain the sum of the magnetic flux linkage angular velocity and the rotor angular velocity; calculating the rotor current set values under the two-phase static coordinates of a rotor; respectively subtracting the rotor current set values under the two-phase static coordinates of the rotor with the rotor current under the two-phase static coordinates and obtaining the reference value of the rotor voltage under the two-phase static coordinates through the calculation by utilizing a performance requirement (PR) controller; and generating the switching signal of a control power device. The rotor current control method has the advantages that the rotor current oscillation of a double-fed induction generator (DFIG) resulted from power grid faults can be effectively inhibited, the grid in-service operation of the double-fed wind driven generator, and the operation performance of the DFIG under the power grid faults is enhanced.

The invention belongs to the field of controlling a wind driven generator power conversion device and relates to a method for controlling a double-fed wind driven generator in power grid faults. The method comprises the following steps of: calculating a rotation angular velocity, calculating a stator voltage, a stator current and a rotor current under two-phase static coordinates, calculating a stator magnetic flux linkage and calculating d, q shaft stators voltage and stators current under synchronous rotational coordinates, calculating a slip-frequency angle and a slip-frequency angular velocity, calculating d, q shaft stators current under rotational coordinates, calculating a stator reactive power, calculating a rotor decoupling compensatory voltage, acquiring the actual values of a double frequency component and a triple frequency component of the rotor current after guiding the d, q shaft rotors current under rotational coordinates to flow by two band-pass filters and advanced delaying rings, acquiring the compensatory items of the double frequency component and the triple frequency component by two PI controllers after subtracting the actual values from the preset values of the double frequency component and the triple frequency component, summing the two compensatory items, acquiring a preset value of the rotor q shaft current under rotational coordinates and the reference values of d, q shaft rotors voltages under rotational coordinates by calculating with the PI controller after subtracting a preset value of the rotate speed from the actual value of the rotation angular velocity, calculating a rotor voltage under the two-phase static coordinates, and generating a switching signal for controlling a power device. The invention can efficiently prevent DFIG rotor current oscillation caused by the power grid fault, realize the on-line running of the wind driven generator and promote the running performance of the DFIG in power grid faults.

The invention relates to a method for identifying on-line parameters of a linear induction motor, which realizes the closed-loop control of exciting current component and thrust current component of a motor and enables the exciting current component to be equal to the thrust current component under the directional control of an indirect magnetic field. The method comprises the following steps: adjusting a secondary time constant value used in a motor controller and changing the specified slip frequency and the synchronous frequency of the motor in the controller by an on-line identification arithmetic to adjust the synchronous angle for the magnetic field to locate; searching the minimum value of the input current of the motor in a steady-state operation condition when the load torque is kept constant, enabling the secondary time constant used in the motor controller to be approximate to the real value of the secondary time constant of the motor, therefore realizing the on-line identification of the secondary time constant of the motor. The invention can realize the correct directional control of the indirect magnetic field of the linear induction motor without depending on other motor parameters hard to be controlled exactly through on-line operation, avoid influence of end effect, parameter change and the like on the control performance, does not need the input voltage component of the motor and improves the practicability of a parameter on-line identification system.

The invention belongs to the field of control of power conversion devices of wind driven generators and relates to a control method of a double-fed induction generator (DFIG) under a power grid voltage three-phase symmetrical drop fault. The control method comprises the following steps of: calculating a stator voltage, a stator current and a rotor current under a two-phase static coordinate system; calculating the magnetic flux linkage as well as stator voltages and stator currents of a shaft d and a shaft q under synchronous rotation coordinates; calculating a slip frequency angle and a slip frequency angle velocity; calculating stator currents of the shaft d and the shaft q under the rotation coordinates; calculating active power, reactive power and electromagnetic torque of a stator; calculating a decoupling compensation voltage of a rotor; obtaining a primary component actual value of the rotor current after the rotor currents of the shaft d and the shaft q under the rotation coordinates pass through a band-pass filter and a lead lag link on the basis of a compensation target, obtaining a difference of the primary component actual value and a primary component set value and calculating through a PI (Proportional-Integral) controller to obtain a primary component compensation item; calculating a set value of the current of the rotor shaft d under the rotation coordinate system; obtaining a difference of a rotation speed set value and a rotation angular rotation speed actual value and calculating through the PI to obtain a set value of the current of the rotor shaft q under the rotation coordinate system; calculating to obtain a reference value of the rotor voltages of the shaft d and the shaft q under the rotation coordinate system; and calculating the rotor voltage under the two-phase static coordinate system and generating a switch signal for controlling a power device.

The invention discloses a water-cooled magnetorheological soft start device, and belongs to the technical field of mechanical power transmission. The device comprises a drive rotator structure and a driven rotator structure, wherein a plurality of drive cylinders and driven cylinders are respectively plugged on drive cylinder sleeves and driven cylinder sleeves at intervals; the drive cylinder sleeves and the driven cylinder sleeves are respectively connected with left magnet-conducting shaft sleeves, right left magnet-conducting shaft sleeves, drive shafts and driven shafts through bolts; a sealing measure is arranged at each connection position; left magnetic yokes and right magnetic yokes are fixed with a magnet-conducting shell; magnet exciting coils and magnetic isolation discs are arranged in the left magnetic yokes and the left magnetic yokes; left bearing seats and right bearing seats are respectively fixed on outer sides of the left magnetic yokes and the left magnetic yokes;left bearings and right bearings used for bearing the drive shafts and the driven shafts are respectively arranged in the left bearing seats and the right bearing seats; a water inlet, a water outlet, a groove, a liquid injecting opening and a liquid discharging opening are formed in the magnet-conducting shell; a liquid injecting plug screw and a liquid discharging plug screw are arranged on theliquid injecting opening and the liquid discharging opening; and a plurality of groups of rotating sealing rings are arranged in the groove. The water-cooled magnetorheological soft start device has the advantages of compact structure, large transmission torque, high radiating performance, high slip frequency power and wide slip frequency range.

The invention discloses an asynchronous motor rotor broken bar fault judgment method with electric signals and vibration signals integrated, which belongs to the field of motor fault judgment. The method comprises the following steps: an acquisition instrument acquires voltage and current data through a current clamp and a voltage clamp, current spectrum analysis is carried out, if the current signals are normal, no broken bar fault happens to the motor rotor, and if the current signals are abnormal and when one side band appears at each position with a twice slip frequency difference from a power frequency, the next step is carried out; voltage spectrum analysis is carried out, if the voltage signals are normal, no broken bar fault happens to the motor rotor, if the voltage signals are abnormal and when one side band appears at each position with a twice slip frequency difference from the power frequency, vibration signal analysis is carried out, and whether broken bar fault happens to the motor is judged. In view of the problem that error judgment exists in a motor current signal analysis method in the asynchronous motor rotor broken bar fault in the prior art, a mode of sequentially judging the stator current, the stator voltage and the vibration signals is adopted, the rotor broken bar fault is detected, and the error judgment rate is reduced.

The invention discloses a method for online computing a motor optimal operating point. Online computing on the optimal operating point of an asynchronous motor is completed through optimal slip frequency corresponding to the optimal operating point of the asynchronous motor. The optimal slip frequency w2_max is obtained by the following formula, Rs represents stator resistance, Rr represents rotor resistance, and Lm represents mutual inductance. The method has the advantages of being high in real-time performance, high in precision, good in system stability, strong in anti-interference capacity and the like.

Because of the necessity of resolver for detecting a rotating position, which is very expensive, and noise suppression of the rotating position signal line on a doubly-fed machine, cost increase of the generator and reduced reliability due to possible failures are inevitable. In order to solve such problem, a generation system in the present invention is equipped with an exciter that estimates the slip frequency of the doubly-fed machine from each primary current I₁ and voltage V₁ and secondary current I₂ and voltage V₂ of the doubly-fed machine and excites the secondary of the doubly-fed machine at the estimated slip frequency.

The invention relates to a method for measuring the time constant of an asynchronous motor rotor on line. The method comprises the following steps of: giving initial parameters in advance; obtaining induced electromotive force of a rotor flux linkage on a stator winding; processing the induced electromotive force of the rotor flux linkage on the stator winding to obtain a value of synchronous angular speed; obtaining a value of slip frequency from the synchronous angular speed; and obtaining a value of time constant of the rotor according to a slip frequency formula. The invention further relates to a device for implementing the method for measuring the time constant of the asynchronous motor rotor on line. The method and device for measuring the time constant of the asynchronous motor rotor on line, disclosed by the invention, have the beneficial effects of simple algorithm, small occupying area on CPU (Central Processing Unit) resources and higher precision of measured time constant of the rotor.

The invention relates to the technical field of power transmission and provides a finished automobile starting method based on a P2 hybrid power transmission system. The method includes the steps that the pressure of a hybrid clutch C0 is controlled to be increased to a control pressure value required for eliminating a gap between friction plates; the torque of a motor is output to an engine through the pressure of the hybrid clutch C0; the pressure of the hybrid clutch C0 is controlled to be adjusted to the small pressure, and the engine is controlled to be automatically ignited and started; the rotation speed of the engine is gradually reduced by increasing of the pressure of the hybrid clutch; when the rotation speed change rate of the engine is smaller than a preset change rate threshold value, the slip frequency of the hybrid clutch C0 is controlled to be gradually reduced; the pressure of the hybrid clutch is increased according to a preset slope; and the pressure of the hybrid clutch is controlled to be increased to the maximum locking pressure, the engine and the motor are controlled to jointly drive a finished automobile to be started, so that the finished automobile is smoothly started in a pure engine mode, and the cost for the engine to start the motor is saved.

The present invention relates to a self frequency conversion solid state laser based on neodymium doped gadolinium calcium oxborate crystal, compromising a self frequency conversion crystal composed of NdxGd1-xCa4O(BO3)3 wherein x is from 0.001 to 0.2, a pumping source, and a laser resonator. The self frequency conversion crystal is cut along a direction perpendicular to the frequency conversion phase match direction of the crystal, and two light-through end surfaces of the self frequency conversion crystal are polished; the pumping source is a laser with wave length from 802 to 815 nm, 830nm, or from 868 to 887 nm, and the laser resonator realizes a unity feedback of the fundamental frequency light and a unity output of the frequency conversion light; wherein the laser resonator is set in front of a pumping source output optical path, the self frequency conversion crystal is arranged in the laser resonator, and the pumping mode is an end surface pumping mode or a side surface pumping mode. The self multiplication frequency, self sum frequency, self slip frequency or self parameter oscillation laser output of different fundamental frequency light can be obtained through determining the optimal frequency conversion phase match direction of the crystal in different fundamental frequency wave lengths and designing the corresponding laser cavity mirror membrane transmittance. The solid state laser is small in size, compact in structure, and stable in performance.

The invention discloses a device and method for testing the thickness of a lubricating oil film of a rolling bearing. The device comprises a high speed motorized spindle and a low speed motorized spindle which are arranged opposite to each other in the radial direction of a support, the front end of the high speed motorized spindle is connected with a rolling element, the front end of the low speed motorized spindle is connected with a ring body of the bearing to be tested, and the rolling element applies radial loads to the ring body of the bearing to be tested through a loading mechanism; the high speed motorized spindle and the lower speed motorized spindle are respectively provided with a speed measurement sensor which is connected with a data acquiring and processing system through a frequency converter; a lubricating device is arranged beside the position of contact between the ring body of the bearing to be tested and the rolling element to change the lubricating status; an ultrasonic sensor is attached to the inner surface of the ring body of the bearing to be tested and connected with a sliding ring by a signal line through a clamp and a hole formed in a pull rod, signals are transmitted to the ultrasonic data acquiring and processing system, and real-time film thickness values of a test point in the contact position of the rolling bearing can be acquired under the action of slip frequency factors with the ultrasonic film thickness measurement technology.

The invention discloses a rolling friction-wear testing machine capable of controlling friction coefficient and slip frequency on line. The rolling friction-wear testing machine comprises a lower sample shaft platform and an upper sample shaft platform, wherein the lower sample shaft platform is provided with a first transmission shaft by a first bearing pedestal, the power input end of the firsttransmission shaft is connected with the power output end of a first motor, and a lower sample is arranged at the power output end of the first transmission shaft; a second transmission shaft is arranged on the lower sample shaft platform, the power input end of the second transmission shaft is connected with the power output end of a second motor, and the second transmission shaft is also provided with a driving transmission gear; the upper sample shaft platform is rotatablely arranged on the second transmission shaft by a fourth bearing pedestal, a third transmission shaft is arranged on the upper sample shaft platform, the power input end of the third transmission shaft is provided with a driven transmission gear meshed with the driving transmission gear, and an upper sample is arranged at the power output end of the third transmission shaft. By using the testing machine disclosed by the invention, rolling friction-wear tests under different slip frequency can be easily realized.

The invention relates to a control method on stable operation for wind electric field of double-fed asynchronous generator which belongs to technology field of power supply. Its steps are: (1) in the electric system of wind electric field containing double-fed asynchronous generator, multiple wind generating sets are equivalent to one wind generating set with constant power. Condenser is linked to the terminal of the wind generating set to compensate reactive power in steady state. Simultaneously, synchronizing generator and double-fed asynchronous generator are connected with the high-pressure side of the wind generator through Delta/Y transformer separately. (2) rotor current control of double-fed asynchronous generator: rotor current of the double-fed asynchronous generator is confirmed by AC slip frequency. Based on controlling the rotor current, the amplitude and displacement of its stator and the output active or reactive work of the double-fed asynchronous generator are controlled, which will stabilize the output of the wind electric field. The invention can minimize the influence on stable operation of electric system after introducing the wind electric field.

The invention provides a slip frequency vector control method for an asynchronous motor. By the method, the problem that an actual slip angular speed is deviated from the set slip angular speed in the conventional method is solved; an increment of a motor slip angular speed which changes along with a rotor side parameter of a motor is added by a model adaptive method; the set slip angular speed is modified by the increment and the slip angular speed in a motor control model is adjusted to be close to an actual value, so that the problem that a rotor magnetic field is not positioned accurately because the rotor side parameter changes can be solved; and therefore, the robustness over motor parameters of a control system is greatly improved.

The invention provides an electric power generating system and a control method thereof, and the system and method provided by the invention are used for solving the defect that the existing electric power generating system which centers on a synchronous motor has less possibility of maintaining constant frequency output when a prime motor operates in a speed change mode. According to the invention, the frequency of an alternating current excitation power supply which is output by a first frequency conversion device is controlled to be always equal to the slip frequency of a first motor according to the preset frequency of three-phase alternating current which is output according to the rotation speed of a first motor rotor and a first motor stator winding so as to adapt to the variations of the rotation speed of the first motor, thus the variations of the rotation speed of the first motor are matched with the optimal rotation speed of the prime motor, the speed change constant frequency output of the electric power generating system is realized, simultaneously the efficiency of the electric power generating system is improved, and the static state and transient state stability of the electric power generating system are improved obviously.

The invention relates to a torque controllable accident vehicle braking force detecting device. An asynchronous motor and an electromagnetic slip frequency clutch are matched to form a slip motor, torque dynamic loading is conducted by using the slip motor, so that the braking torque of an accident vehicle brake is obtained, and accident vehicle braking performance is evaluated. The device comprises a detecting device (A), a supporting device (B) and a guiding device (C). The detecting device (A) delivers the torque generated by the slip motor to a force exerting chuck, a proportional integration differentiation (PID) controller is used for controlling outputting of variable torque, and a brake braking force curve is obtained. The supporting device (B) is connected with the detecting device through an upper supporting plate in a rigid mode and is matched with the guiding device through an upper guide track smoothly. The guiding device (C) controls the detecting device and the supporting device to move vertically through a linear guide track. By means of the torque controllable accident vehicle braking force detecting device, the problem that braking force of accident vehicles which do not meet road testing or platform testing detecting conditions can not be detected is solved, and meanwhile the anti lock braking system (ABS) performance of automobiles is evaluated.